Candida albicans is a member of the normal flora of mucosal surfaces that usually exists in a commensal relationship with the host unless the flora is perturbed or the immune system compromised when this fungus an become opportunistically pathogenic. Immunosuppression resulting from infection with the human immunodeficiency virus (HIV) leads to oral and vaginal candidiasis in over 90% of patients with AIDS. Mucosal defense is mediated principally by secretory immunoglobulin A (SIgA) antibodies which inhibit adherence of C. albicans. HIV infection results in the progressive depletion of CD4+ T lymphocytes and disruption of the follicular dendritic cell network in germinal centers. 60% of all lymphocytes are found in the mucosal-associated lymphoid tissues that are the inductive sites for SigA antibody responses and memory. The objective of this application is to define the salivary and vaginal secretory immune responses to C. albicans in men and women with AIDS. Sequential samples of saliva and vaginal secretions and isolates of C. albicans will be obtained from HIV+ men and women and healthy controls during a four year longitudinal study. Data will be analyzed to test the following hypotheses: (1) The susceptibility of AIDS patients to oral and vaginal candidiasis results from impaired SigA antibody responses due to disregulation of the immune system; (2) Strains of C. albicans colonizing AIDS patients are more virulent, genetically less diverse than those in healthy subjects, show tropism for the mouth or vagina and persist in these habitats. The Specific Aims are: Aim 1A. Determine the levels of total SigA, SigA1 and SigA2 subclasses in saliva and vaginal secretions of AIDS patients. Total SigA,SigA1 and SigA2 will be quantitated using an enzyme-linked immunosorbent assay (ELISA) specific for exocrine IgA to test the hypothesis that progressive AIDS results in reduced concentrations of SigA and its subclasses in saliva and vaginal secretions. Aim 1B. Analyze the quantity and specificity of total SigA, SigA1 and SigA2 antibodies reactive with C. albicans in saliva and vaginal secretions. The specificity and quantity of antibodies will be analyzed by Western blotting and by ELISA to test the hypotheses that the quantity and specificity of antibodies changes throughout the progression of AIDS. Aim 1C. Analyze the avidity of total SigA, SigA1 and SigA2 antibodies reactive with C. albicans in saliva and vaginal secretions. Chaotrope dissociation ELKISA and immunoblots will be used to test the hypothesis that progressive AIDS results in the production of low avidity antibodies that do not exhibit affinity maturation and are ineffective in immune elimination of this fungus. Aim 2. Compare the SigA proteinase activity of C. albicans isolates from the mouth and vagina and t he levels of proteinase in saliva and vaginal secretions. SigA-degrading enzymes will be detected by a radial diffusion assay and by ELISA using proteinase-specific antibody to test the hypothesis that these enzymes contribute to the virulence of this fungus by destroying SigA antibodies. Aim 3: Compare the genetic diversity of C. albicans isolates obtained from the mouth and vagina. DNA fingerprinting will be used to test the hypotheses that in AIDS patients there is; (a) limited genetic heterogeneity within the strains of this species isolated from the mouth and vagina; (b) different genotypes of Candida in the mouth compared with the vagina and (c) genotypes of this fungus are stable in these habitats over time.